[llvm-bugs] [Bug 34647] New: llc version 4.0 and later takes up to 45 times as long to compile shader code for Mesa

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34647

            Bug ID: 34647
           Summary: llc version 4.0 and later takes up to 45 times as long
                    to compile shader code for Mesa
           Product: new-bugs
           Version: 4.0
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: bcrocker at redhat.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 19167
  --> https://bugs.llvm.org/attachment.cgi?id=19167&action=edit
Vertex shader bytecode

The Piglit (OpenGL test suite) ext_transform_feedback-max-varyings test
utilizes somewhat unusual shader programs (both vertex and fragment shaders).

The llc compiler prior to 4.0 compiled these programs in
not-unacceptable times of 0.078 seconds for a representative
vertex shader and 2.6-4.5 seconds for a representative fragment shader.

The V4.0 and later llc takes a MUCH longer time to compile the same
code: 1.66 seconds for the vertex shader (a factor of 20 times slower!)
and 1 minute 55 seconds for the fragment shader (a factor of 25-45 times
slower!).

I will attach sample vertex shader code (ir_draw_llvm_vs_variant0.bc)
and fragment shader code (ir_fs914_variant0.bc).

The target architecture is PPC64LE.

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